With a wedding ring on her finger and a party endorsement on her back, Kanako Otsuji is on a mission to become Japan's first openly gay member of parliament and change the way the country treats sexual minorities.

In a political world whose upper ranks are almost exclusively older men, the 32-year-old Otsuji stands out for more reasons than her sexual orientation.

Just weeks ahead of the July 22 elections, Otsuji, who is running on the ticket of the largest opposition Democratic Party of Japan, tied the knot with her partner.

But as Japan does not recognise gay marriage, her ceremony Sunday is considered illegitimate in the eyes of the state.

"By serving as a politician who is openly lesbian, I can make the homosexual population a visible issue," said Otsuji, formerly a local lawmaker in the western city of Osaka.

"I believe one of my missions in parliament would be to expedite legislation of a system similar to a civil union," Otsuji said in an interview at a campaign office in Tokyo's biggest gay district.

She predicted, however, that "it would take at least 10 years of debate" before Japan allows civil unions, a system which would give the rights, benefits and recognition of marriage to same-sex and unmarried couples.

"Right now, Japan doesn't even allow married women to have dual surnames," she said.

In Japan, homosexuality has long been accepted in fact but not openly discussed.

In medieval times, homosexual relationships were an open secret among priests, nuns and samurai knights. More recently, vibrant gay entertainment areas have sprouted in major cities.

But even if gays and lesbians do not encounter outright hostility, Otsuji said Japan was behind many Western countries in awareness of sexual diversity.

She doubted the Liberal Democratic Party of Prime Minister Shinzo Abe, who often calls for Japan to re-embrace "family values," would endorse a gay candidate.

"There are gay politicians and there must be gay members of the Liberal Democratic Party, too, because it is such a big party," she said. "But I cannot imagine the LDP would endorse an openly gay candidate."

Gay circles in Japan welcome Otsuji's candidacy.

"I think more gays and lesbians of younger generations will start contesting in the field of politics and I hope Otsuji will lead the movement," said gay activist Satoru Ito, who offers counselling and workshops for young homosexuals.

"Many gays and lesbians in Japan are still struggling to come out."

Otsuji herself struggled with years of dilemma and fear until she finally accepted to herself at age 23 that she was a lesbian.

"I would see many homosexual people come out only at gay bars and pretend to be heterosexual during the day," she said. "Even at gatherings of gays and lesbians, they didn't want to use their real names" in fear of their families and straight friends finding out.

"I didn't think it was right that you are forced to hide who you really are."

After university, she went to work as an intern for an Osaka lawmaker. Otsuji hesitantly confided her sexuality to her but was thrilled when the politician agreed to raise the subject of sexual minorities in the assembly.

"Politicians openly deliberated words that had only been whispered and heard at underground gay bars," she said. "That was when I became determined to enter politics."

In another bid to increase awareness for gays and lesbians, Otsuji and her partner, who is one of her campaign aides, held a public marriage ceremony in which both of them wore white wedding dresses.

Otsuji said she had never thought of doing something as conservative as a wedding.

"But I was simply happy to see so many people celebrating my wedding," she said. "Living as a lesbian, there haven't been many opportunities for people to celebrate my life."

Some 1,000 people gathered for the event, part of a gay festival in a park in the central city of Nagoya. Leaders of her party including Ichiro Ozawa, Japan's main opposition leader, sent congratulatory telegrams.

But while Abe is facing sagging approval ratings due to a scandal and mismanagement of the pension system, Otsuji's path to office will not be easy.

Only around 10 percent of members of parliament are women, placing Japan 100 out of 138 countries in female representation according to the Inter-Parliamentary Union.

Despite its endorsement of Otsuji, the Democratic Party of Japan does not mention sexual minorities in its election manifesto.

Otsuji admitted her candidacy will also be a test for the party.

"If I fail this time, Japanese politics may not have another gay candidate for 20 to 30 years," she said.